Circuit integrity indicating system



Get. 36, 1951 c. M. HINES 2,573,442

CIRCUIT INTEGRITY INDICATING SYSTEM Filed July 2, 1 949 s SheetsSheet 1 INVENTOR- CLAUDE M. H

AT TORNEY Get. 36, 1951 c. M. H|NES 2,573,442

CIRCUIT INTEGRITY IVN'DICATING SYSTEM Filed July 2, 1949 3 Sheets-Sheet 2 CLAUDE M. HINES ATTORNEY 0a. 30, 1951 c. M. Hl NES 2,573,442

CIRCUIT INTEGRITY INDICATING SYSTEM Filed July 2, 1949 3 Shets-Sheef 3.

IN V EN TOR.

CLAUDE M. HINES ATTORNEY Patented Oct. 30, 1951 CIRCUIT INTEGRITY INDICATING SYSTEM Claude M. Hines, Verona,-Pa., assignor to Westinghouse Air Brake Company, a. corporation of Pennsylvania Application July 2, 1949, Serial No. 102,836

16 Claims.

This invention relates to a circuit checking means, and more particularly, to an apparatus adapted to be associated with the control circuits of electro-pneumatic brake apparatus employed on a train of cars and to selectively signal the integrity or lack of integrity of the said con- .trol circuits or other electrical devices associated system and an entirely pneumatically controlled automatic braking system, each of which is controlled by the same control lever mounted on a single brake control valve device. Such brake control valve device is shown and described. in Patent No. 2,106,483 of E. E. Hewitt which is assigned to the assignee of this application.

The automatic brake system consists of the usual brake pipe extending throughout the train with a branch pipe leading from said brake pipe to a brakecontrol valve device on each car of the train. The said brake pipe is charged with fluid under pressure and it is the variation of pressure of said fluid which causes the operation of the brake control valve device on each car to effect either a brake application or a brake release as desired. The variation of fluid pressure in the brake pipe travels by wave action, at a speed somewhat less than that of sound in air, from thepoint of origin, usually the locomotive, to all other parts of the train. This wave action effects a serial action of the brake control valve devices 'on the cars for sequentially applying or releasing the brakes on successive cars of a train. The serial brake action results in a slack action between the cars of the train accompanied in some instances by shock and jerking of the cars which is undesirable especially in the case of passenger trains.

The electro-pneumatic straight-air brake control system, which makes use of electricity to control the brake operation, produces practically simultaneous and uniform control of the brakes on" all cars. The simultaneous and uniform action of the brakes as a result of instantaneous transmission of the electrical control impulses throughout the train, minimizes the slack action between the cars and produces faster applications of the brakes, thereby enabling shorter stopping distances wthan may be obtained with the auto.-

ima c b ake con ol sy t m- For convenience, the electro-pneumatic straight-air brake control system will hereinafter be referred to as the straight-air brake system, and the wholly pneumatically controlled brake system will be referred to as the automatic brake system. i v

Because of the advantages inherent in the straight-air brake system over the automatic brake system, the straight-air brake system is customarily employed in preference to the latter system. The automatic brake system thus serves as an alternate brake system to be used iri'most instances in the event of failure or a faulty condition of the straight-air brake system;

The present straight-air brake systems employ control wires or circuits which extend from the locomotive or control car at the head end of the 7 train through all cars in the train, suitable electric couplers being provided between the cars for serially connecting each corresponding car-wire into one continuous conductor through the train. By reason of flying ballast, rain, snow and the lost motion between the individual cars, the electric couplers are vulnerable to faults, such as open circuits, shorted or grounded circuits which may cause failure of the straight-air brake sys tem to function either partially or even completely. If the nature and location of the fault can be determined, it is in most cases possible to restore the straight-air brake system promptly to its full service-ability without the loss of its utility.

The straight-air brake system usually includes two magnet valves, commonly referred to as the application magnet valve and the release magnet valve, on each car of the train. The release magnet valves are first operated upon the initiation of a brake application, to close a port to atmosphere from a pipe extending from car to car and throughout the train and commonly known as the straight-air pipe. The application magnet valvesare next operated to admit fluid under pressure from a suitable source local to each car,

tion magnet valves to supply fluid under pressure p to the straight air pipe during a. straight-air application of the brakes, reduces the rate of build-up of braking forces, but does not alter the degree of the application for the reason that the straight-air pipe is continuous and the operative application magnet valves are effective to establish the proper straight-air pipe pressure.

The failure of a small percentage of the release magnets to operate during a straight-air application to close their individual exhaust communications from the straight-air pipe to the atmosphere is, however, a matter of grave concern. In

-;the:,-time necessar Eto determinea .faulty straightazirirbrake equipment -by-;attempting .astraight-air application before :resorting to the automatic ahra-lse :system.

The desirability of continuously indicating the integrity erslack offintegritymf the electrical conitrol :circuits :and of the magnet valve windings yin electro-pneumatic 'brakecontrol systems has :previously recognized and various means and methods have been proposed and employed iforithiszpurpose. One :such method is described -in1my .-prior copending application Serial No.

25,208, filed' Mayj, 1948.

The copending application Serial No. 25,208 'provides an apparatus adapted for use in coniunction with electro-pneumatic brake control "systems and constructed on the Wheatstone Bridge principle with the application magnet windings and the release magnet windings each servingas one branch of individual Wheatstone Bridge arrangements, said bridge arrangements "being automatically intentionally balanced and unbalanced periodically so'long as the integrity -01 the electro-pneumaticbrake control system is unimpaired. The apparatusdescribed in the said application Serial No. 25,208 provides for check- 'ing. the integrity of the brake control circuits only while the brakes are released.

Itis an object of my present invention to ,provide an improved circuit-checking apparatus of the-type .disclosed in the above-mentioned application, characterized in that it includes means FfOl' detecting faults in the electrical control cir- .cuits, or in the windings .of magnet valves asso- :ciated therewith, :in :such a manner as :to indicate the location of any iau-ltsin the system not .only while the brakes are released, but also while the Ibrakes are applied.

"It is another object of my present invention to "provide an improved circuit-checking apparatus of the type referred to in the foregoing object and further characterized in that it includes one means for detecting faults in the electrical control circuits while the brakes are releasedand a second means for detecting faults in the electrical control circuits while the brakes are applied.

Another object of my invention is to provide an improved circuit-checking apparatus, of ..the type referred to ,in the fore oin Objects, ,charaoterized in havingnovel means for disconmecting said i bridge arrangements fromand reconnecting them to the brake control circuits 4 when the brakes are applied and released, respectively.

In the circuit-checking apparatus disclosed in the above-mentioned copending application, the certainty of the apparatus giving a correct indication of the integrity of the control circuits being checked when there is no fault in the said control circuits depends ,upon the Wheatstone Bridge arrangements being automatically inftentionally balanced and unbalanced periodically. However, if a brake application is prolonged the-release,magnet windings may become heated by the energizing current and consequently the resistance of these windings may increase-enough to efiect an unintentional unbalance of the bridge arrangement when the control'circuits arereconnected to the bridge arrangement during a brake release. It is an object of my present invention to provide an improved circuit-checking apparatus of the type :mentioned above, for preventingthe occurrence of *such faulty indications and characterized in that it includes means for separately electrically heatinga'branch of the Wheats'tone Bridge other than thatcontaining the release magnetwindings whilethe release magnet windings are ener-- gized'during abrake application. By thus uniformly varying the resistance of corresponding arms of the Wheatstone Bridge arrangement, unintentional unbalance of the bridge arrangement is prevented.

In the circuit-checking apparatus of my abovementioned copending application, the-automatic intermittent unbalance of the W heatstone' Bridge arrangements is produced by short-circuiting first one'branch andthen another branch of the bridge.

Another object of my invention is to provide an "improved circuit-checking ap aratus of the type referred to in the foregoing objects ,and characterized in that it provides maximum fiensibility to automaticallyintentionally unbalance the bridge arrangements periodically by shortcircuiting first two opposite branches and then ;two other opposite branches of the bridge.

The a ve jects to the with oth r b ects wh h wi b mad appa e t in the su s qu nt description of my invention, are attainfid by apparatus to 'be hereinafter described when read in onnection with the accompa yin drawing wher in Figs. 1. '2 and 3 when ta n to ether. constitut .a diagrammatic viewshowine a simplified brake control equipm nt f lway rs .a-nd trains embodying my novel circuit-checking andv signalling system.

While asimplified brake .control equipment is shown ,in the drawings for the purpose-bf -illustrating the nature and utility of my novel circuit-checking system, it will be understood that the apparatus illustrated and described herein .is intended to and may be applied to and tunetion with conventional brake control equipment as .well .as various other types of control circuits.

The brake control equipment shown in Fig. -1 .is that required for the locomotive or traction vehicle of a train, and may include a brake valve 1, an equalizing discharge valve 2, a vent valve device 3, a magnet valve device 4, amase ter switch device 5.12m appl cation and re ease ma n va ve devi e 6, automaticbrake c n-- trol device 1], an abrake cylinder The brake valve device i is preferably the same "as, or similar to, that described in Patent "No. 2,106,483 of E. E. Hewitt dated January-25, 1938 son it is deemed necessary to describe briefly only those functions of the brake valve device helpful to an understanding of the operation of the brake equipment illustrated.

The brake valve device I is preferably operated by movement of a handle 9, in a single application zone, to control all applications of the brake. In order to accomplish this, the brake'valve is provided with a selector II], which in one of its two positions conditions the brake valve for straight-air. brake operation, and which, in the other of its two positions, conditions the brake valve for automatic brake operation.

When the selector I3 is in the straight-air position, and the handle 9 is in release position, the straight-air control pipe II is in communication with the atmosphere, through a port in the brake valve while the brake pipe I2 is being maintained charged from a main reservoir I3, under the control of a feed valve I4 by way of a feed valve pipe I5 and a branch pipe I6. A straight-air application of the brakes is effected by moving the handle 9 to any desired position in the application zone, whereupon cornunication between the control pipe II and the atmosphere is closed, and fluid under pressure is supplied to this control pipe to a degree dependent upon the degree of movement of the handle 9 into the application zone. During this movement of the handle 9, the brake pipe I2 continues to be maintained charged from the main reservoir I3 to a pressure regulated by the adjusted setting of the feed valve I4.

When the selector I0 is in the automatic position, and the handle 9 is in the release position, the straight-air control pipe II is connected to the atmosphere and the brake pipe is charged as before described. When it is desired to effect an automatic application of the brakes, the handle 9 is first moved to a first service, or slack-gathering position, in the case of long trains, and then to full service position. If the train is short in length the brake valve handle may be moved to the. full service position in the first instance. In the first service position of the brake valve handle a slow rate of reduction of brake pipe pressure results, and in the full service position, brake pipe pressure continues to be reduced at a service rate until the handle is returned to the lap position. The degree of reduction in the brake pipe pressure is thus controlled according to the duration of time in which the handle 9 remains in the full service position. During this manipulation of the handle, the straight-air control pipe II continues to be connected to atmosphere.

Regardless of what position the selector II! is in, if the handle 9 is turned to an emergency position, the brake pipe I2 will be vented to the atmosphere directly, by'the operation of a separate valve device within the brake valve.

The functioning of the brake valve I will be more fully understod from the description of the equipment operation which will follow hereinafter.

The equalizing discharge valve device 2 is embodied in a casing containing a piston I'I subject, on its upper side to the pressure of fluid in chamber I8 and on its lower side to the pressure of fluid in a chamber I9. Attached to the piston I! is a stem having one end thereof slidable in a bore 2I. The stem 20 is recessed at 22 to receive the end of a lever 23.' The lever 23 is pivotally-mounted on a pin 24 attached to the casing and has an extension 25 for operating an exhaust valve 26. The exhaust valve 26 is normally biased to a seated position by a spring 21, but upon counter-clockwise movement of the lever 23 about pin 24, the vent valve 26 is unseated in equalizing reservoir 33 by a branch of pipe 29.

Operation of the equalizing discharge valve device is effected by reducing the pressure of fluid in chamber I8 and in the equalizing reservoir 30, whereupon the piston I! is shifted upwardly due to the unbalancing of fluid pressures in the chambers I8 and I9. The upward movement of the piston I'I rotates the lever 23 in a counterclockwise direction about thepin 24 to unseat the vent valve 26. As will appear more clearly hereinafter, unseating of the exhaust valve 26 allows fluid under pressure in chamber I9 to flow to atmosphere until the presure therein becomes slightly lessthan the'pressure in chamber I8 and in the equalizing reservoir 30, whereupon the pistion I I is returned by the unbalanced fluid pressures to the position shown wherein the exhaust valve 26 is seated by its spring 21. Since the chamber 9 is connected to the brake pipe by way of a branch pipe I6, pipe 3I and vent valve device 3, as willbe more fully described, it follows that any reduction of pressure in chamber I9 will effeet a corresponding reduction of the pressure in the brake pipe and that the brake pipe pressure reduction can be controlled in accordance with the degree of reduction of the pressure in the equalizing reservoir and in chamber I8.

The vent valve device 3 comprises a casing containing a piston 32, subject on the one side to the combined pressures of fluid in chamber 33 which is in continuous communication with pipe 39, and that of a spring 34, and subject on the other sideto the pressure of fluid in a chamber 35, connected atall times to the branch pipe I6. A restricted port 36 in the piston 32 permits the fluid pressure in chamber 33 to normally equalize with that in chamber 35 so that the spring 34 is effective to shift the piston 32 to its lower or normal position. Attached to the piston 32 is a valve 31 which is held on a seat rib 38 by the force of the spring 34 when the pressurein the two chambers 33 and 35 is equalized.

In the lower-most position of the piston 32, a communication is established between the brake pipe I2 and the pipe I6 leading to the brake valve. The chamber 33 above the piston 32 is connected by pipe 39 to the brake valve device I and by a branch of pipe 39 to the magnet valve device 4. Upon the release of pressure in the pipe 39 and in the chamber 33, the overbalancing pressure in the chamber 35v shifts the piston 32 to its upper position, wherein the communication between the pipe I6 and brake pipe I 2 is cut oif and the brake pipe I2 is connected past the valve 31 and the seat rib 38 to the atmosphere through a large port 49. This rapidly reduces the brake pipe pressure, to cause an emergency application of the brakes, as will hereinafter be described.

The-.magnet valve device 4- is embodied in a casingrhaving therein a valve II which is urged toward an zunseated position :by azspring :42 and actuated to a seated position upon energization .of an electro-magnet 43. When the electromagnet 43 is deenergized, the spring 42 unseats valve 4| to establish a communication between the branch of pipe 39 and the atmosphere through a port 44. As long as the electro-magnet 43 is energized, the valve 4| is held to its seat and the communication between the pipe .39 and the atmosphere through port 44 is closed.

The master switch device 5 comprises a casing containing two flexible diaphragms 45 and 46, disposed therein in spaced coaxial relationship and connected by a stem 4-1. At the outer side of the diaphragm 45 is a chamber 48 connected to the straight-air control pipe ll. On the outer side of diaphragm 46 i a chamber 49 that is connected to a straight-air pipe 50. The two diaphragms 45 and 46 and the casing define a chamber 5| between the diaphragms through which the stem 41 extends.

Two movable contact members .52 and 53 are disposed in chamber 5| and rigidly secured to the stem 41 by an insulating spool 54, the contact member 52 being known as the release contact member and the contact member 53 being known as the application contact member. Both contact members are adapted to move with movement of the stem 41 from th position shown toward the right, that is, in the: direction of chamber 49, to first efiect an engagement of the release contact member 52 with a pair of resilient contact members and 56. A further movement of the stem to the right efiects engagement of the application contact member 53 with a pair of resilient contact members 51 and 58. The resilient contact members 55, 56, 51 and 58 yield under pressure to permit continued movement of the spool 54 and the contact members 52 and 53 after engagement with the resilient contact members. The resilient members 55 and 58 are connected to a wire 59 which is connected to the positive terminal of a supply battery 60 by a supply wire 6|. The resilient contact member 56 is connected to a release control wir 63 hereinafter referred to as the release wire. Engagement of the contact members 55 and 56 by the contact member 52 results in energization of the release wire. The resilient contact member 51 is connected to an application control wire 62, hereinafter referred to as the application wire. Engagement of the contact members 51 and 58 by the application contact member 53 results in energization of the application wire 52.

Contained in the chamber 49 is a spring supported stop member 64 which is'engaged by the stem 41 at a point in the travel of the stem in which the release contact member 52 engages contact members 55 and 56 and before engagement of the application contact members 51 and 58 by contact member 53. This spring stop serves to stabilize the switch device against any tendency of a pumping action and to define a socalled lap position thereof.

The application and release magnet valve device 6 comprises a casing containing a supply valve 65 normally urged into seated position'by a spring 66 and actuated to an unseated position by energization of an electro-magnet S1. The supply valve 55 is effective when seated to interrupt communication between the feed valve pipe I5 by way of a branch pipe 68 and. a chain ber 69 in the application and release magnet valve device 8. When unseated. the supply valve 5! permits the flow of fluid under pressurcirom the branch pipe 68, past the valve 65 to the chamber 59 to which the straight-air pipe 50 is connected. Also disposed in the magnet valve device casing is a release valve 10 which is normally urged to an unseated position by a spring 1| to connect the straight-air pipe 5|! to atmosphere via a port 13 and actuated into a seated position by energization of an electro-magnet 12.

One terminal of the electro-magnet 61 is connected by a branch wire 62a to the application wire 62 which extends through the train. The other terminal is connected by a branch wire 14a to a battery return wire 14 connected to the negative terminal of the supply battery 60.

One terminal of the electro-magnet 12 is connected by a branch wire 63a to the release control wire 53 which extends through the train. The other terminal of the electro-magnet 12 is connected by the branch wire 14a to the battery return wire 14. Energization of the application and release electro-magnets 51 and 12 is thus controlled by the master switch device 5 as will be explained hereinafter.

The automatic brake control device 1 comprises a casing having therein a piston 15 subject on one side to the pressure of fluid in a chamber 16, and on the other side to the pressure of fluid in chamber 11. The piston 15 is provided with a stem 18, which is recessed to receive, and to move with movement of the piston, a graduating slide valve 19. The stem 18 is further provided with collars and BI so spaced as to engage a main slide valve 32 between said collars with a slight amount of lost motion.

The chamber 15 is connected by a branch pipe 83 to the brake pipe I2. The chamber 11, in which is located the stem 18 and the slide valve 82, is connected by a branch pipe 84 to the auxiliary reservoir 85. The parts of this automatic brake control device are illustrated in what is known as the brake release position, in which the auxiliary reservoir 85 and the slide valve chamber 11 are charged with fluid under pressure from the brake pipe l2 by way of the branch pipe 33, chamber 16 and a feed groove 85, which in this position of the piston 15 connects the chambers 1B and 11. In this release position of the slide valve 82, a cavity in the slide valve connects a passage and pipe 81 leading to a double check valve 88, and to the brake cylinder 8 during an automatic brake application, to an atmospheric port 89 for the release of fluid pressure in the pipe 81 and the brake cylinder 3. With the brake pipe l2 and the auxiliary reservoir charged with fluid under pressure, a reduction of the brake pipe pressure effected as will hereinafter be described, at a rate sufficient to create the necessary pressure differential across the piston 15 causes the piston to be shifted to the left or in the direction of chamber 16. The initial movement of the piston and the graduating valve 19 uncovers a service port 98 in the main slide valve 82, the piston simultaneously closing the feed groove 86, and thereby cutting off communication between the chambers 16 and 11. The continued movement of the piston 15 by reason of the brake pipe reduction causes the collar 8| on the piston stem to engage the slide valve 82 and move it to a position in which the service port registers with the port and pipe 81. Communication is thus established through which fluid underpressure is supplied from the auxiliary reservoir 85 past the valve element (not shown) of the double check valve 88 to the brake cylinder 8 to establish fluid pressure therein, thereby applying the brakes. As the auxiliary reservoir pressure is reduced by flow of fluid under pressure therefrom to the brake cylinder, in effecting the brake application, the unbalance of forces in effect across the piston is diminished and when the auxiliary reservoir pressure is reduced slightly below the pressure in the brake pipe and connected chamber 16, the piston and the graduating valve will be moved in the right-hand direction, towards chamber 11, to a so-called lap' iliary reservoir pressure willcause the piston; 15

to move the main slide valve '82 into release position, in which it is shown, again connecting the brake cylinder to the atmospheric port 89 and opening the feed groove 86 to permit a recharge of the auxiliary reservoir.

The equipment just described is a simplified combined automatic and straight-air brake control equipment such as maybeapplied to the locomotive. For simplicity the brake control apparatus for the cars is not shown in the drawings, but it should be understood that the equipment on each car may include devices similar to the device on thelocomotive such as an application and release valve device 6, an automatic brake control device 1, an auxiliary reservoir 85, and a brake cylinder 8. The automatic brake control device I on each car is connected by a pipe similar to pipe 84 to receive its supply of fluid pressure from the auxiliary reservoir on each car or from a separate supply reservoir charged from the brake pipe on the respective car.

The electro-magnets 61 and 12 on the cars are connected in a manner similar to that shown for the locomotive, namely to the application wire 62, release wire 63, and to a common return wire, all of which extend from the locomotive through each car to the last car of the train. The respective application and release magnet valves on the locomotive and all cars of the train are thus controlled simultaneously by selective control of energization of the application and release wires.

In order to better understand the nature and operation of my circuit-checking apparatus, .a brief description of the operation of the electropneumatic brake control equipment thus far described will be helpful. Assuming that the main reservoir [3 is charged with fluid under pressure, and that the selector I0 is'in the straight air operation position, the apparatus thus far described will operate as follows:

With the brake valve handle 9- in the release position, the fluid from the main reservoir l3 will flow, at a pressure regulatedby the feed valve 14,

through the usual rotary valve (not shown) of the brake valve l to the pipe l5, thence by way of 16 at the face of piston '15 of the automatic brake control device 1 on the locomotive and similar devices on each of the cars in the train. With no pressure in the auxiliary reservoir, brake pipe 76 -'-=the release magnet p Fluid under pressure in brake pressure chamber 16 will'force the piston to the position in which it is shown whereirrthe feed groove 86 is opened to' allow communication" w from the chamberlfi' to the chamber 11 and'to' the auxiliary reservoir 85; After suflicient charging' time, the auxiliary reservoir 85' on'the -1000-" motive and all the cars of the train will becharged with fluid at'a pressure equal to "the b ral e pipe pressure as regulated by the feed h valve I 4. At the Same'time this equalizing of fluid v the brake valve l to pipe 29 leading tothe equal 5"-'-izing reservoir 38"and'to chamber I8 abovethe' equalizing piston [-1, With the brake pipe pres sure, by way of pipe 3|, active in chamber!!! below-the equalizing piston ll, of'equal'valueto'the f equalizing reservoir pressure in chamberlB, the gfi weight of the piston'lTtogether with the force of spring 2'! acting against theexhaust valve26 will maintain-the exhaust valve on its seat. In'thisi releasepositionof the brake valve handle'9, the

straight-air control pipe H 'is connected through gg 'the self-lapping portion (not shown) 'of'the brake valve 1 to the atmosphere. The brake cylinder Ben the locomotive and on each car in the train attached to the locomotive may be connected to the f atmosphere either through the gfj pipe 81, the cavity in the slide valve 82 and port 89 in the control device 'L'or may be connected throughthe straight-air pipe to'the'magnet" valve device Sand thence to atmosphere by way of the unseated exhaust valve In and port 18in 'To efiect straight-air application of the brakes, the handle '9 is moved fromthe release position into-the application zone toward the full service position to an extent according to the desired de-" 0* gree of application of the brakes.

With the selector II! in the straight-air opera-g tion position, the self-lapping portion of the brake valve device is operative to control the flow of fluid under pressure from the feed valve pipe I5 m) the pipe H and thence to chamber 48 of the master switch device 5 to a value proportional to the degree of movement of the handle 9 into the application zone. Fluid under pressure in cham ber 48 will cause the spool 54 to move to the right d through the medium of the stem 41 thus closing cation and release magnet valve device 6, as before described, to establish a pressure in the straight-air pipe 50 equal to the pressure in pipe H and chamber 48. Since the straight-air pipe is connected by way of the double check valve 88 to thebrakecylin'der 8, it follows that fluid under pressure will be established inthe brake cylinder equal to the pressure of fluid in the straight-"air pipe. f I

The degree of application may be increased ing the brake valve handle further away from release position into the application zone,

and may be decreased by moving the handle back I toward the release position.

When it is desired to efiecta release of the? brakes, the brake valve handle 9 is placed init'srelease position whereupon fluid supplied to pipe II and to chamber 48 is released to'theatmos phere by the self-lapping portion of the brake I valve. Fluid pressure in the straight-air pipe 50,; f and hence in the brake cylinders, is effective in cha ber v tf' membersts' a t no tnqi ogtact. Ifi P i 4 nd h f p i iei n m @175 d sa'rro the contactmember 53' by'mo've nien't'oi the SPCOi 54 to the" left thereby controlling the pplicatiori and release magnet" valve device 6 to release the straight-lair pipe and brake cylintier pressures to the atmosphere.

"When it is desire'dto efieot an application of thebrakes by automatic operation, the selector I0 i} moved to th"a utomatic position. Then. "the brake pipe and auxiliary reservoirs about the train charged with fluid under a 'e'regulated by the setting of the feed valve H, as before described, the handle 9 is moved fifom the'release position through a lap position, intoftne service position. In this'ser vice position ofl'thfhandle' 9 the brake valve operates in the usual manner to a sconnectme' branchpipe l aiidith edualiziiig reservoir pipe 29froin theieed valvepipefi; 5150 to connect the equalizing discharge: pipe 213 tothe' atmosphere andthe equalreservoir to ex aust through a restricted passage (notfshov'vnfin the brake valve, Fluid up r' pressure iii the equalizing reservoir 30 and chamber l8 of the equalizin discharge valve device" 2 thu reduces, to atmospheric pressure at aj'coirtrolled rateduring all the time the handle Sis 'infthe service position." As soon as the desired degree of reduction" of equalizing reservoir presj effected, the brake valve handle 9 is reinanually to the lap position. The reauction in fluid pressure in' chamber I 8 results in auunbalance of preg'ssure across piston I] with the result the piston movesupwardly unseating valve it thereby reducing brake pipe pressure to the atmosphere untilthe brake pipe pressure iS reduced'to a pressure equalto the reduced value ojj the'equalizing' reservoir pressure.

When'a' reduction in brake. pipe pressure is effected, a corresponding reduction of fluid pressureltakes place inch'amber 'ltjof the brake contrh' device '1 on the locomotive and each car of; the train The unbalance of pressures on the piston causes saidpswn to shift to the left toi'the service "position which turn causes graduating 'valve TQ andIsIide valve 82 to-rnove t0 tlie right through the medium of stem 1 8 and collarlil so that fluidpressure irom the auxiliary reservoir is connec'ted mange the slidevalve port 9!! to'th'e brake cylinder 8 until auxiliary reservoir fluid pressure is re'duce'drto a fluid pressure correspo cling to slightly'les's thanfbrake pipe pres siir'e/Whenthe piston li will becausedby the uhbalance of fluidpressures acting on it, to'rnove totheright to the lap position wherein thegradu: ating valve 19 coversthe service port 90 to cut; off further flow of auxiliary reservoir pressure to thebrake cylinder.

Itwill be obvious that the degree of the brake application is controlled accordin'g'to the degree of reductionin the equalizing reservoir, pressure; and that'a graduated control of thebrakes is ob tainable by proper manipulation of the: brake va vefhandle.

Toefiect a release ofthe brakes following an automatic application, the brake valve handle 9 'ismoved to'the release position in which the brake pipe pressure isrestoredffrom; the main reservoir in a manner similar to that explained previously in the chargin'g' of the-equipmena' The increasingbrake pipe pressure is efiective'in the automatic brake. control device I to. force the piston L5 .to the release position which the x iary ser ir. i echa ged ith fli aues cr o cit d t racin oi. h re ease pres re. f om. brake c ne thm en ice ove:

wcham er 11 a d s te stand; the brake fi f Pressure is connected to the 'atinosphereby way or double check t ove at; pipe 8.1 and port as;

An emergency application of the autor'nati c brakes may be efiectedmanuall'y by'movement'or the brake valve handle to emergency position, in which position the automatic brake valve is posif tioned in such a manner as'toconnect the pipe It to the atmosphere through a large port (not shown) in thefbrakej valve; or by removal of the operat r an f m t e br v l e. 'lia lc i the well-known manner'of deadmanfi control. In this latter insta'nce, fluid pressure is released from pipe 35, and'chamber 3.3. ofv the vent valve device 3 through the brake valve. The ii uic'ljpres-w sure acting on piston 31 .is unbalanced by'reason of the loss of fluid pressure in chamber 33, and the piston 32 thus, moves. upwardly to cut' on"; communicationfrom pipe l6. to'bi'ake'pipeffl and atthe'same time connect brake pipe 12 to theatmosphere, through the large port 40 to efiect, reduction or fluid pressure'therein at arapid rate.

An em rgen y application of the automaticbrakes may be further effected automatically by deenergization of the magnet valve device 4;

The magnet valve 4 is shown normally energized by a circuit from the supplybattery tp, controlled by a speediresponsiv'e switch 8! and; as will be explained later, by the circuit cheching equipment constituting myinvention. fle energi zation oi the'magne'tvalve iby any'cause such as, loss of supply, current, operation of either the speedcontrolled. switch or the circuit-checking; equipment will result in the venting oi fluidpre ssure from chamber 33 of the vent valve device. 3 and in an emergency venting of brake pipe pressure to the} atmosphere.

Emergency venting o'i the brake pipe pressure results'in brake pipe pressurebe'i-ng quickly re duced to atmospheric pressure, Such a reduction in fluid pressure in chamber 1.6 of; the automatic; brake control device 1 results in movement of the piston 75, to; the-application position and an equalization of auxiliaryreservoir pressure into. the brake cylinder 8, thus producing an application of the brakes with maximum force.

According to my invention, the circuit-checking, and;signallingapparatus, which I propose-to; use;inconjunctionivvith the above described brake c ntro1 equipment, to; indicatethe operative-con.- d ich i hema con rolircui s and to e ct, n. auto at applica i n c brakes h u the operator attempt a straight-air brake appli cation when the electrical on rol ircui are faulty, isshqwn; injFigs; 23 and3*- This circuit,-

" motive and-cachettheldifierentcarsin the train:

che kin ppar tus; ompr s e sential y a WheatstoneBridae arrangement for. each of the two brakecontrQLcircuit to'h checked; ItlWill. be recalledtthat the brake equipmentjust described'employs two control circuits, namely (1).

the release control circuit comprising the release.

62: and the common returnior ground wire with the application. electro magnet 61 on the 1000- nnected npara lelrthereb etwem cire t check n equipment, comprises wo Sim ar Whcat tcu B d e arrange nts- 9?; i width itebriqsearr cecmcut saz eina apnl cdr 13 to the application control circuit and the bridge arrangement 93 being applied to the release control circuit. These bridge arrangements together with the necessary cooperating relays and indicating signals are included in an equipment case 94 with the necessary lead wires, as identified hereinafter for connecting to the train wires, and to the signals, etc. Each bridge arrangement comprises the usual four branches, one of the branches including the control circuit to be checked.

Specifically, the Wheatstone Bridge arrangement 92 includes as one branch thereof a fixed resistor 95, and a second branch including in series a fixed resistor 96 and a temperature compensating resistor 91. In order to effect a balance in the bridge, the resistor 95 should be of a value equal to the sum of the values of the resistor 96 and resistor 91. A small adjustable resistor 98 is placed between these twobranches to adjust for manufacturing differences of the values of resistors 95, 96 and 91 and thus keep the resistance valves of the two branches equal. The temperature compensating resistor 91 may be located remotely of the case 94 so as to be subject to the atmospheric temperature and not influenced by locomotive cab or control car temperature where the checking equipment may be located. Automatic compensation for changes in control circuit resistance due to atmospheric temperature variation is thus accomplished. The resistor 91 is connected into the bridge branch by suitable leads 99 and I00 between the resistor and suitable binding posts IOI and I02 on the equipment case 94. A condenser I03 carried within the case 94 is connected in parallel to the resistors 96 and 91 and serves to prevent any inductive efiect of current variations in the bridge circuit from influencing the bridge balance condition.

Another or third branch of the bridge arrangement 92 includes the application magnet control circuit. This branch includes wire I04, a resistor I05, switch contact member I0uof a relay I01 hereinafter to be described, wire I08, binding post I09 on the case, lead IIO to the application train wire 62, then over the various application electro-magnets 31 in parallel, to the l common wire 212, binding post H2 on the case 94, wire H3, resistor H4, and wire H5, to the junction I20.

The fourth branch of the bridge arrangement ment is joined to the opposite end of said resistor. The fourth branch is joined to the. first branch at the resistor 95 and the third branch is joined to the second branch of the bridge at the junction of condenser I03 and wire I04. The third and fourth branches are joined at the junction I20. 5

The variable resistor I24 in the fourth branch of the bridge is of a value equal to the resistance ofthe application electro-magnet 61 on the locomotive when the contact arm I25 is positioned at the extreme right-hand position registration,

. l4 with tlie'O position indicated on the escutcheon plate I28. With the resistance of the locomotive brake control equipment in the third branch of the bridge'thus matched inthe fourth branch,

the resistor I24 and contact arm I 25 can be calibrated such that the ostensible number of application control magnet windings in the train brake control equipment can be determined by adjusting the contact arm I25 on the resistor I24 until the bridge arrangement is in a balanced condition.

Two current limiting resistors I29 and I30 are placed in series in the voltage supply circuit for the bridge arrangement. Resistor I30 is variable and is adjusted in accordance with the voltage applied to the checkin equipment in excess of the voltage for which the equipment is designed so as to protectthe bridge from being subject to too high a voltage.

When the number of cars in the train is reduced to merely one or two, there is a possibility that the voltage drop across the electromagnets on the few cars, as supplied from the checking equipment, may be sufficient to cause the magnets to operate undesirably. In order to prevent this possibility, two like variable resistors I32 and I3I are placed in parallel with the third and fourth branches respectively and adjusted to a value simulating the resistance of the application electro-magnets of a predetermined number of cars, say two, so as to cause the total application control circuit resistance, when only one or two cars are in the train, to be'suificiently low that the voltage drop across the application electro-magnets due to current supplied from the checkin equipment is insufiicient to cause the undesired operation of the magnets.

The bridge arrangement 93 is similar to the bridge 92, comprising the usual four branches, one of the branches including the control circuit to be checked, in this case the release control circuit. Specifically the bridge 93 includes as one branch thereof a fixed resistor I33, and a second branch including in series a fixed resistor I34, wire I35, switch contact member 136 of relay I01, wire I31, temperature compensating resistor I38, and wire I39. A small adjusting resistor I40 is placed between these two branches to adjust for manufacturing diiferences for a similar reason as that of resistor 98 explained previously. The temperature compensating resistor I38 serves the same purpose for bridge 93 as resistor 91 does for bridge 92. The two temperature compensating resistors 91 and I38 are mounted together in a case I4I located in such a position as to be subject to the same atmospheric conditions as the magnets on the train. The temperature compensating resistor I38 is connected into the bridge branch by suitable leads I42 and I43 between the resistor and suitable binding posts I44 and I45 on the equipment case. A condenser I46 carried within the case 94.is connected across the leads I42 and I43 to said binding posts so as to parallel the resistor I38 and serves to prevent any inductive eifect of current variations in the bridge circuit from influencing the bridge balance condition.

Another or third branch of bridge arrangement 93 includes the release magnet control circuit. This branch includes switch member I41 of relay I01, wire I48, resistor I49, wire I50, switch member I5I of relay I01, wire I52, binding post I53 on the case 94, lead I54 to the release train wire,

then over the various release electro-magnets 12,

7 am parallel, to the common wire 212, binding post game II.2.;.wires; I:I3-,.resistor; I.I4-, and wires I ISz-to' the junction: I20..

The. fourth: branch of. the" bridge: arrangement 93icompriseswire. I55, variableresistor I55; wir.e*-

I51,.Variable resistor. or. rheostat. I58, having a 5 manually. operable contact arm I59, wires I60;

I213. H9; fuse. H8; contactmember: IIJ; wire I'IG.

to vthe junctionIZI]; The contactarm 59.=.is"positioned. manually tov indicate. thenumber of cars asshownon the escutcheonplate I6I.

The first branch of the bridge 93, namely-1e sistor I33;. is. joined: toone end: ofl resistor I49 while the second branchisjoined :tothe opposite end-.of. thexsaid resistor. The fourth. branch is:

joined to the first branch otthe bridge. arrange ment-.at-:the.junction of resistor I33 and :wire: I55. and; the third: branch. is joined to; the. second: branch at. the. switch. member I41 of. relay; I01: The third and fourth branches .aretjoinediatlthei. junction. I20.

The :variable resistor. I58-in..the,fourth branch. of v thee-bridge isof. a .valuesequalto the. resistance of; the. release. electro=magnet 12. on.the .locomo+- tive when the contact arm. I59. is positioned'to:

16 contact member I13of relay I13; wire I80? re sistor I8I,andwire I82Lto wire I26 oran-al'tei nate circuit which includes wire I14, contact member. I83 of relay I16; resistor I8I and Wire'- I82. towire I26:- These associated circuits; so calledLcoding. circuits; are so arranged under cer-- tainconditionsdescribed later as to alternately shortecircuit first the second. and fourth branches-of the-bridge simultaneously and-then the first andthird. branches to-produce an in tentional unbalanced condition thereof. It. shouldzbenoted; that .due to the short-circuiting ofgtwo. branches. simultaneously a maximum un'-- balanceis-obtained thereby obtaining a maxi mum: sensitivity.

The associated circuits.- of bridge I 93 are substantially identicalto those of bridge 92- and it deemed. unnecessary, therefore to describethese, sorcalled. coding circuits of bridge 93 m m detail as .they maybe understood fromthe-pre vious description of the associated circuits of the bridge arrangement 92;

The reference; numerals I84 to I99 inclusiveg" are thusapplied without repetitive description:

the extreme right-hand. position in registration. to. identify the associated circuits of the-bridge with the. Oposition. as. indicated .on .the. escutcheon plate. I 6 I Withthe. resistance; of the locomotive. brake. control. equipment. in the. third branch .of thebridgecthusmatcheddn the fourth.

branch, the resistor I51 and .contactarm I59. can

be calibrated such that. theostensiblenumber ofrelease. control. magnet windings. in the train brake. control equipment. can. be determined .by. adjustingthe. contact. arm. I59 on the. resistor.

I 58 .until .thebridge arrangementis in .a balanced condition.

Two currentlimiting resistors I62 and. I63..are; placedin seriesv in. the voltage. supply. circuit. for thebridge;arrangement.. Resistor. I63.is yariableand is adjusted in accordance. with .the. voltage. 4 Q

applied-.to. the. checking equipment. in excess. of 1 the. :voltage for which. theequipment is designed. so asto protect the bridgefrombeing subject to. high .voltages.

Fora purpose similar. to .that.of..resistors I32- andj SI 9 in bridge-arrangement 92', two. likevaria-rbleresistors I64 and I65 areplaced in .the bridge arrangement 93,-inparallel with .the. third and. fourth branches respectively, .to. prevent the undesired, operation of... the. release .magnets; when the,nurnber.of .cars. in .the train is low sayone. or. two. It will be apparentthat bypreventing such; undesiredoperation. of..the application and.re--. lease. magnets simultaneously; the .undesired apev plication of the brakesis prevented;v On bridge 92, operativelyresponsive/to a balanced and .unabalanced. condition. of the bridge. circuits and. connected inseries between wires. I 21 .and.;I 04 is a detector relay; ISI-Iand an electricemeter' I6.1.;. suchas an .ammeter of thezero-center-type. The.- meter I61 is normally short-circuitedqbyia circuit including a wire I68, normally closedswitchcom tact member I69 of a manually;operableyswitch: I10 hereinafter described; and wire I047; to. ree

move theresistance of; the; meter from the relayj circuit during the automatic. o eration of the; bridge arrangement.

Further associated-with the bridge=92 is a circuit whichmay include either wire I1I, contact;

member I12 of aarelay I13 to be; described, later,

arrangement93, in consecutive order correspond ing totheapplication of the numerals I66 tend inclusive-tothe associatedcircuits of the bridge- 92 except cases where the: elements ofthese circuits are commontoboth of thev bridge-er rangements.

A two-winding. polarized relay. 200 is asso ciated with, the. relays IB6,,. I 13, I16- and I84' and cooperates. withthese relays toprcduce acoded signalof agiven frequency when .the two con trol circuits .beingchecked retaintheir fidelity, as: will be explained later. under Operation, This relaygflweincludes the. windings 20I and2I12fiandJ the contact members 203, 2% and 205.- Finergization of winding 20I will cause the relay con-'- tact members tosassume the right-hand position and energization of winding. 262-: will cause the contact members to assume the left-hand posi tion. Relay; 200 being ofthe polarized type,

- energization.,. of either: winding need 1 only be Therelay I66 includes thecontact members 206 and 201.

Contact members 298 and 291 arefront and'fback contact members,- respectively. The. front contact member 28ft isactuatedifroma.dropped-out or open position to a picked-up .or closed position when the-wind--- ing ;of:therelay. is energized, and the back-con'- tact-member 201 isactuated from a dropped-out"- or.closed position to a picked-up or open position* when the winding of the relay is-energ-ized 50.; Relay I84 is identical in construction to relay-I66 andiincludes front contact member 298 anda back contact member 209.

The relay!" includes the front contact mem-- bers-l19, I12; "15,189, 2H3, ZII and 2I2; all of which are actuatedto a closed position when the-- relayis-energized, but are delayed in dropping-- out responsive to deenergization of the winding Of the relay I13, due to a delaying circuit de scribed hereinafter. Relay I16 is identical in construction and operation to relay I13 and" cludesthe front contact members-I15,' I83, N12, I99; 2I3', 2I4and 2I5. A delayed dropping out characteristic is imparted to the contact-mem'-' bers of the relay I16 bya delay circuit similar" is.a cir cuit..which may inc1ude either-wire-I18, ittothat provided for--rel'ay--I13.

This circuit-checking equipment further includes a signal relay 2I6 having the front contact members 2I1, 2I8, and 2I9 and the front and back contact members 228 and HI. The term "front and back means that the contact members have one closed position when the relay winding is de-energized and a different closed position when the relay winding is energized.

The relay I81 comprises two separate windings 222 and 223. Winding 222 is normally energized to actuate the relay to a picked-up position. Winding 222 is energized by means of circuit extending from positive battery wire 6|, by way of wire 224, 3+ terminal post 225, contact member 226 which is combined with contact member I I! to comprise the manually operated double-pole-single-throw switch 221, fuse 228, wire 229, wire 230, temperature compensating resistor 215, winding 222, wire 23I, wire H9, switch contact member H1, 3-, terminal post 232 and to negative battery wire 14.

The second winding 223 of the relay I91 is included in a circuit extending from the release control wire 63 b way of lead wire I54, terminal post I53, Wire I52, winding 223, wire 233, wire H9, fuse H8. contactmember H1, and wire H6 to terminal post 232 and thence to negative battery wire '14. The current flow through the winding 223 produces a magnetic effect in dominating opposition to that of winding 222 so as to cause the relay I01 to assume a deenergized or dro ped-out position when the windings 222 and 223 are simultaneously energized. This operation occurs upon the initiation of a brake application at the instant the release contracts of the master switch 5 are closed and will be more fully explained later.

Relay I 81 further includes the front contact members I96, I5I, 234, 235 and 236 and the front and back contact members I36, I41 and 231.

Still another relay 238 is included in the checking equipment. Relay 238 comprises two separated windings 239 and 245 as well as two front contacts 256 and 251. Winding 239 is normally energized to actuate the relay to a picked-up position by means of a circuit extending from posi-'- tive battery wire 6|, to wire 229 as previously traced, thence by way of wire 3| I, wire 248, normally picked-up contact member 229 of the relay 2I6, normally picked-up contact member 234 of relay I91, wire 24I, winding 239, wire 242, resistor 243, wire 244, wire H9. and thence to negative battery wire 14 as previously traced.

The second winding 245 of the relay 238 is energized during a brake application to actuate the relay to a picked-up position. As previously explained upon initiation of a brake applicationv the two windings 222 and 223 of relay I81 are so energized as to cause the contact members of said relay to assume the dropped-out position. Contact member 234 being one of said contact members is therefore not picked-up as is normal, but is dropped-out, thus opening the energizing circuit previously described of the lower winding 239 of relay 238. For reasons explained hereinafter, it is desired to maintain relay 238 in a picked-up position unless a fault indication is present. This is done by use of the second winding 245 of relay 238' which is energized during a brake application in response to the voltage drop produced on a potentiometer resistor H4 connected acrossthe terminal posts H2 and 232 to which are respectively connected the'common return wire 212 and the batteryre turn wire 14. Specifically the circuit for ener-'- 18 gizing winding 245 may be traced from wire II 3 connected to one end of resistor H4, by way of wire 246 variable resistor 241, variable resistor or rheostat 248 having a movable contact arm 249 which is operated in tandem with the contact arm I59 of rheostat I58, as indicated by the broken line, wire 258, winding 245, and wire 25I to the other end of resistor H4. The voltage drop across resistor I I4 may be varied to regulate the drop-out voltage of the relay 238 by adjusting two variable resistors 254 and 255 which are in parallel with resistor I I4.

Relays I81, 2I6 and 238 through their contact members, previously mentioned, control the signal lamps 258 and 259 on the equipment case 94, together with and in parallel with signal lamps 268 and HI on a separate panel 262 in the operators cab. An audible signal such as a buzzer device 329 is also provided in conjunction with the signal lamps and is actuated during a fault under control of contact 220 of relay 2I6. The circuit for energizing buzzer 328 extends from battery supply wire 229 by way of wire 3I I, wire 248, contact member 229 which will be in its lower position during a fault, wire 3I8, terminal post 3I9, buzzer 320, wire 32!, and terminal post 3I6 to battery return wire I I9.

The switch I 10 comprises the contact members I69, I81, 265 which are normally biased to their closed positions as by resilient spring forces in the contacts themselves or by a separate spring 210 operatively associated therewith. Switch I19 also comprises a contact member 266 normally biased to its open position by spring force inherent in the contact itself or as by a separate spring 2" associated therewith. The switch I10 has a handle 261 which is manually operative from a normal central position to a position to one side of the normal position for moving contact members I69, I81 and 265 to their open positions against the spring force and to the opposite side of the normal position for closing the contact member 266 against the spring force.

A pneumatic switch device 268 is also provided having a normally closed contact member 269 in parallel with the contact member 2 I9 of the signal relay 2 I6 across wires 213 and 214 which form a circuit including the magnet valve device 4 and the switch device 9I. The pneumatic switch is controlled by fluid pressure in the straight-air control pipe I I and is arranged to open the contact member 269 when the said pressure exceeds a predetermined low pressure, such as five pounds per square inch. The switch device 268 causes magnet valve device 4 to operate to effect an automatic emergency application of the brakes in the event that a control circuit fault exists at a time that a straight-air application is initiated as will be fully explained hereinafter. Supply battery voltage is provided in this circuit checking apparatus from the positive battery wire (H by way of lead 224, terminal post 225, switch member 226,- fuse 228 to wire 229; To avoid needless repetition hereinafter in tracing circuits, the wire 229 will be referred to as the battery supply wire," and circuits traced by reference thereto.

Also, wire H3 being connected to a common. return wire 212 for the magnet circuits through=- out the .trainat the binding post II2 will be referred to as the common wire.

Operation :In preparing the circuit-checking apparatus for operation; the operator first moves the switch 221 to-a position where the contact members'226 and H1 are both inthe closed position, thereby connecting the battery supply wire 229 andthe battery return wire H9 to the battery 80 byway of circuits previously'described, the bridge arrangements being correspondingly energized over circuits previously described.

A circuit isestablished from the battery supply wire 229 byway of wire230, a current limiting-resistor 215,-winding 222, of relay I01, wire 23I "to battery return wire H 9, for energizing the winding 222 thereby actuating the relay I01 to'a picked-up condition in which'the front contact members I06, -II, 2'34, 235, 238 are closed and (front andlback contact members I36, I41 and 231-are'in their upper closed positions. A circuit-is thusestablishedfrom the battery supply wire 229 by way of'contact member 238, wire 216 to -wire.21*1,zthence through the resistors I52 and I63 to the resistor I40 at the junction of the first and second branches of the bridge arrangement' 93-and through resistors I29 and I30 to'the resistor-98 at the junction of the first and second branches of the bridgearrangement 92. Parallel circuits are now completed through the first and fourth branches of eachbridge to the junction I20 byway ofwire I26,-wire*I21, wire H9, fuse II8,'switch member I l1aand-wirel I8 on the bridge-arrangement 92,-andby way of wire IEO, wire I21,'wire "I I9, fuse H8, switch :inernber II? and wire H8 on the bridge arrangement-92, and by way of wire I80, wire I21, wire H9, fuse H8, switch member I I1 and wire H6 on the bridge arrangement '93. Parallel circuits are also completed through the second and third branch of each-bridge to the junction I29 by their respective circuits thereby connecting the junction between the third and fourth branches of both bridge arrangements to the negative side of the battery supply 80 by way of-binding post 232 and wire 14.

The operator balances the bridge arrangements by moving the handle 261 of switch I10 into the position for opening the contact members I69, I81 and 265. The contact members I69 and I81 are effective when thus actuated to their open positions to open the circuits, previously described, for shunting the meters I61 and I85 respectively, and the meters will accordingly indicate the condition of balance of the respective bridge arrangements. The contact arms I25 and I59 are then manually adjusted on the resistors I24 and I58 until a zero reading of the meters I61 and I85 is obtained. A balanced condition of the bridge arrangements is obtained, in which condition, the variable resistor in the fourth branch of the bridge is equal to the resistance of the train brake control circuit included in the third branch of the bridge. The position of the contact arms on the variable resistors I24 and I58 should indicate on the escutcheon plate the number of magnet valve devices 6 and correspondingly the number of cars in the train attached to. the locomotive. If this indication does not agree with theactualnumber of cars in the train, afaulty circuit condition is thus indicated. E'or example, .if both contact arms I25 and I59 are positioned to indicate wfifteen cars in the train with the meters I61and I85 indicating zero, when in realitythere are eighteen cars-an indication is given that the train line connector between cars fifteen'and sixteen is separated, or-that the common wire 212 is open between-cars fifteen and sixteen. If one of the contact arms is positioned to indicate fifteen cars and the other contact arm is simultaneously positioned to indicate eighteen cars in the train with the meters indicating zero, the indication is that the control circuit included in the bridge arrangement giving the fifteen car indication-is open between-cars fifteen and sixteen. v

A grounded control circuit, or a short-circuit between a-control wire and the returnwire-causes an indication of more cars in the train than there actually is and, in-certain instances-makes it impossible to balancethecorresponding bridge arrangement bycontactarm adjustment on its respective resistor.

Assuming that contact member 204 of relay 200 is in its left-hand position as-shown on the drawing, a circuit will be completed which enables the condenser 218to be charged. This circuit for charging condenser 218 consists of wire 211, wire 219, resistor 280, wire-2B1, contact member 204 in its left-hand position and wire 282 'to the condenser 218, the opposite side of which is connected to the batteryreturn wire -I I9 by way of wire 283.

The bridge arrangements having been balanced, the relays I68 and I84 are deenergized. A circuit is now completed for energizing the winding of relay I13 via wire 219, resistor 280, wire 28I, the back contact members 201-and 209 in serial relation, wire-284, contact member203 of relay 209 in its left-hand position, wire 285, the winding of the relay I13, wire-286,-contaot member 285, and wire 283 to the battery return wire II9. Relay I13 is accordingly actuated to a picked-up condition in which the front contact members 119,112,495, I89,2I9, 2H and M2 are in closed position. The second and fourth branches of both bridge arrangements are each thereby short-circuited by the following-shunting circuits. The fourth-branch of bridge 92.is

shuntedby way of wire I18, closed contactmember I19, wire I80, resistor-IN and wire I82. The second branch of bridge'92 is shunted by way of wire I1I, closedcontact member I12 and wire 114. The fourth branch of bridge 93 isshuntedby way of wire I94, closedcontact member I95, wire I98, resistor I91 and wire I98. The second branch of bridge 93 is shunted by way of wire I88, closed contact member I89, wire I90.

It can be seen that when the second and fourth branches of the bridge arrangement 92 are .simultaneously short-circuited, the first and third branches are connected in parallel with each other, and the winding of relay IE6 is subjected to the voltage drop across the first and thirdbranches, thus causing the relay I65 to be ac tuated to a picked-up position. The relay I84 of bridge arrangement 93 is simultaneously actuated to apicked-up position by a similar circuit. With relays I56 and I84 simultaneously energized to their picked-up positions, the back contact members 201 and 209 are actuated to their respective open positions and the front contact members 206 and 208 are actuated to their respective closed positions.

The back contact members 201 and 209 are efiectivein their open positions to interrupt the circuit previously traced for energizing the winding of the relay I13 and the front contact membars 205, 208, 2I0 are effective when in closedposition to establish a circuit consisting of wires 281 and 288 to wire 263 and thence to the battery return wire II9 for energizing the upper winding I of the relay 200 to eiTect movement of the relay contact members 203, 204 and 205 from their left-hand position as seen in the drawing, to their right-hand position. The contacts of relay I13 are not restored to their respective dropped-out positions responsive to interruption of the energizing circuit for the winding of relay I13 by the opening of contact members 201 and 209 as previously described, due to the fact that the condenser 218 discharges through a local loop circuit including the winding of relay I13 and a resistor 292 to thereby maintain the winding of relay I13 energized and the contact members of the relay I13 in the picked-up position for a certain length of time sufficient to permit actuating of the contact members of relay 200 fully to their right-hand positions.

- Movement of the contact member 204 of relay 200 from the left-hand position to the right-hand position first opens the circuit previously described for charging the condenser 218 and then closes a circuit for charging condenser 29I associated with relay I16, such circuit extending from the battery supply wire 229, by way of switch contact member 236, wire 216, wire 211, wire 219, resistor 280, wire 28I, contact member 204, wire 289, wire 290, condenser 29I and wire 283 to the battery return wire II9.

During the period of time in which the contact member 2 I2 of the relay I13 is maintained pickedup by current discharged from the condenser 218, the contact member 205 of relay 208 in its righthand position thereby establishes a connection to wire 293 from battery supply wire 229 by way of relay contact 236, wire 216, wire 294, contact member '2 I2 of relay I 13, wire 295, contact member 205 of relay 200, wire 296, closed contact 231 of relay I01 and wire 291 to wire 293 which lead to theicontact members 266 and 2I8. The purpose of this connection to wire 293 as just described will be made apparent presently.

.After the condenser 218 is discharged and no longer maintains the relay I13 in a picked-up position, the relay is restored to the dropped-out position opening the front contact members I19, I12, I95, I80, 2I0, 2H and 2I2. Contact member 2I2 thus acts to interrupt the circuit connection to wire 293 from battery supply wire 229. With the contact members I19, I12, I95 and I89 open, the circuits for short-circuiting the second and fourth branches of each of the bridges 92 and 93 are open and the bridges are returned to their normal condition. If the resistance of train circuits remains unchanged, as it will if no circuit fault exists, the bridges will remain balanced and the detector relays I66 and I84 will become deenergized, thus opening the front contact members 206 and 208 and closing the back contact members 201 and 209.

The back contact members 201 and 209 are effective in their closed positions to complete a circuit from the supply Wire 211 over wire 219, resistor 280, wire 28I, contact members 201 and 209, wire 284, and contact member 203 of relay 200 in its right-hand position, wire 298, the winding of relay I16, wire 286, contact member 265 of switch I10, and wire 283 to the battery return wire II9. Therelay I16 is thus energized and actuated to its picked-up position in whichathe contact members I15, I33, I92, I99, 2I3, 2I4 :and- 2I5 are in their closed positions. The contactmembers I15, I83, I92 and I99 are effective their closed positions to short-circuit the first and third branches of both bridge arrangements. The first branch of the bridge 92 is short-circuited by way of wire I1I, contact member I15 and wire I11 to wire I2I. The third branch of bridge 92 is short-circuited by way of wire I14, contact member I83, resistor I8I and wire I82. The first branch of bridge 93 is short-circuited by way of wire I88, contact member I92 and wire I93 to 'wire I55. The third branch of bridge 93 is short-circuited by way of wire I90, contact member I99, resistor I91 and wire I98.

It can be seen that when the first and third branches of the bridge arrangement 92 are simultaneously short-circuited, the second and fourth branches are connected in parallel with each other, and the winding of relay I66 is subjected to the voltage drop across the second and fourth branches thus causing the relay I66 to be energized and actuated to a picked-up condition. The relay I84 of the bridge arrangement 93 is simultaneously energized and actuated to a' picked-up condition by a similar circuit. With relays I66 and I84 simultaneously energized and actuated to a picked-up condition, the front contact members 206 and 208 are actuated to their respective closed positions and the back contact members 201 and 209 are actuated to their respective open positions.

The actuation of contact member 2 I3 of relay I16 to its closed position incidental to the pick-up of relay I16, prepares a circuit which is completed by the closing of contact members 206 and 208. Such circuit extends from the wire 219, by way of resistor 280, closed contact members 206 and 208, wire 299, contact member 2 I3, the lower winding 202 of relay 200, and wire 283 to the battery return wire I I 9. Relay 200 is thus actuated to effect movement of the contact members 203, 204 and 205 to their respective left-hand positions, from their right-hand positions.

Contact member 205 is effective in its left-hand position to establish a circuit from the battery supply wire 229 by way of relay contact 236, wires 216 and --294, closed contact member 2 I5 of relay I16, the contact member 205 inits left-hand position, wire 296, contact member 231, and wire 291 to wire 293. The purpose of this connection will be made apparent presently.

The shiftof the contact member 204 from its right-hand to its left-hand position interrupts the circuit previously traced for charging the condenser 29I and establishes the circuit previously' traced for charging condenser 218.

The interruption of the circuit for energizing'the winding of relay I16 due to opening of contact members 201 and 209 is not effective to cause immediate drop-out of the contacts of relay I16 becaus the dropping out of relay I16 is delayed for a predetermined period of time by' the discharging of condenser 29I through a local loop circuit including resistor 300 and the winding of relay I16. As soon as the condenser 29I is discharged, the relay I16 is deenergized or dropped-out, thus opening contact members I15, I83, I92, I99, 2I3, '2I4 and 2I5. The droppingout of contact members I15, I83, I92 and I99 opens the short-circuit paths previously describedfor both bridge arrangements, thus restoring; the bridge arrangements to normal. If the bridge arrangements are restored to 'balanced condition, as they will be if no fault exists gideenergized' andiarerestored to their dropped-out position, thus initiating another cycle of operation as previously described.

From the above description it can be seen that the above described cycling operation of the relays I 86 and I84, I13, I16 and 200 will continue so long as the bridge circuits are restored to balanced condition between successive intentional short-circuitings of the branches of the bridge arrangements. Thus it will be understood that contact member 205 of relay 200 is oscillated between its right-hand and left-hand positions at a frequency corresponding to the frequency of operation of relays I13 and 116. For example, the frequency of operation of relays I13 and I16 may be such that contact member 205 of relay 200 will have a frequency of vibration of approximately 33 vibrations per minute, thus connecting wire 293 to battery supply wire 229 at intervals of two seconds.

With the equipment operating as just described, movement of the control lever 251 of the switch I18 by the operator to a position for closing the contact member 253 results in further operation now to be described. With the contact member 268 closed, an impulse of current will be supplied from wire 293 when connected to battery supply wire 229, at the times previously described, to the winding of relay 2I-6 over a circuit extending by way of switch contact 265, Wire 30 I, current limiting resistor 302, the winding of relay 2| 6, wire 303 to wire 2-83 which is connected to the battery return wire H9, thereby energizing the relay 2I8 and effecting a movement of the contact members 220, 2I1, 2I8, 2I9, 22I to their upper closed positions. With contact member 2 I! thus closed, the impulse of current energizing relay 2 I6 is also supplied to the condenser 303 for charging of same by a circuit including wire 305, contact member 2I1, wire 306, condenser 304, wire 351, cont-act member 235 of relay I01, wire 308, wire 309 and wire 283 to the battery return wire II9. A variabl resistor 3I0 is provided in parallel with condenser 304 to regulate the discharge of the condenser to a predetermined rate. With the condenser 304 charged to battery voltage, it will by reason of the closed circuit from said condenser, wire 305, closed contact member 2I1, wire 305, the winding of relay 2I6, wir 303, and wire 233, hold the relay 2I6 energized for slightly more than a two-second period until another impulse of current is provided over the wire 293.

With the relay ZI E energized and the front contact member 2I8 closed, it will no longer be necessary for the operator to hold contact member 266 of switch I in closed position. Any impulse of current provided on wire 238 will now be supplied by way of contact member 2IB of relay 2H5, wire 30I, and resistor 302 for energizing th winding of relay 2I6 andrecharging the condenser 304. It can thus be seen that so long as the impulses are supplied to the Wire 293 at the prescribed interval of time before the condenser 304 becomes discharged, the relay 2I6 will be maintained energized and consequently picked-up.

While the relay 2! 6 is maintained picked-up, a circuit for energizing the signal lamp 258 is completed from the battery supply wire 220 over wire 3I I, wire 200, contact member 22I of relay 2I5 in its upper closed position, wire 312 and thesignal lamp 258 to the battery return wire I I9. Inparallel with the signal lamp 258 is the" signal lamp 250' on the indicating panel 232 in the cab,

witha lead wire 3I3 connected. to aterniinal 3M which is connected to battery supply by wire 312 as just described, and another lead Wire 3 I 5 C011? nected to terminal 3N5 which is connected to the battery return wire H9. The signal lamps 258 and 280 remain energized to indicate to the operator the integrity condition of the circuits and are deenergized upon the occurrence of a fault in the brake control circuits as presently de-- scribed.

Should a change is resistance of either or all control circuits arise, such changes being caused by failure of magnet windings, couplers, wires;- by loss or addition of cars, short or grounded circuits, etc, the bridge arrangements will not balance when the short circuits of the bridge branches are removed. In such a case, the detector relay I65 or I84 in the respective bridge ar rangement will not drop out. The circuit over contact members 201, 289, wire 2233, contact mendber 203 to energize the selected relay I13 01' I16 is thus not restored. The coding operation of relays I65, I84, I13, I16 and 200 is thereby interrupted and the repeated current impulses, supplied to energize the Winding of relay 2 I5, fail to continue, with the result that the relay 2I5 is restored to its dropped-out position. With relay 2H5 thus dropped-out, the back contact members 225 and 22I are closed in the down position, and the front contact members of said relay are opened in the down position. The contact member 22I, being in the down closed position, is eifective to complete a circuit from the supply wire 229 by way of wire 3I I, wire 240, contact member 22I, wire 3I1, danger signal lamp 259 to the battery return wire I I9, for energizing the danger signal lamp 255. A similar danger signal lamp 26I on the indicating panel 262 is connected in parallel with the signal lamp 259 and therefore will be energized simultaneously with the signal lamp 259. It is seen that at the same time the danger signal lamps 259 and 23I are energized, the clear signals 258 and 280 will be deenergized by the moving of the contact member 22I from the upper closed position to the down closed position. At the ame time, battery voltage is supplied over wire 3, wire 240 to the down closed contact member 220, wire 318, and terminal 3I6 to buzzer 323 or similar audible warning device and thence to the terminal 3 I6 and the battery return wire I I9.

In the event that a fault on the control circuit is indicated, the operator may proceed to determine the location of the fault by operation of switch handle 251 of switch I10 to its position in which, the normally closed contact members I69, I81 and 265 are-in open position.

Contact members I89 and I81 are effective in their open positions to cut in meters I01 and I85 respectively, into operation. At the same time contact member 265 interrupts the connection from relays I13 and I16 to battery return wire I I9, thereby stopping operation of these relays.

Adjustment of contactor arms I25 and I50 may thusbe effected, as previously described, to determine the location of the fault.

If during the time the signal lamps 258 and 260 are energized, the operator initiates a straightair brake application, the release wire 53 will first be energized, as previously explained, and a circuit will be established for energizing the top winding 223 of relay I01, which circuit extends from release wire 63 by way of lead I54, wire I52,

the winding 223 of relay I01, and wire 233 to the battery return wire I I9. Thi energization of top winding 223 opposes the energization of the'bottomwinding 222 which is effected by a circuit extending from the battery supply wire 229 by way of wire 230, a voltage limiting resistor 215 and 231 are shifted to theirlower closed position.

When the front contact member 236 is actuated to its open position, the circuit previously explained for energizing the bridge arrangements 92 and 93 and the relays I13 and I16 from the battery supply wire 229 are interrupted thereby discontinuing the previously described cycling operation. The contact members I06 and II,

are actuated to their respective open positions during a straight air brake application for the I a 20 the application train wire 62 and the release train purpose of preventing any flow of current from wire 63 respectively, to the bridge arrangements 92 and 93 which would prevent the normal opera tion of the application and release magnet valve devices 61 and 12'. This precaution is taken since any current fiow in the third branches of the bridge arrangements may prove harmful to the bridge arrangements by grounding out through the resistors I32 and I65 to wire i21 and thence to the battery return wire.

The back contact member 231 closes a circuit from the battery supply wire 229 by way of contact member 251 of relay 238 which is energized and thereby actuated to its picked-up position, as explained hereinafter, and back contact member 231 of relay I01, wire 291, closed contact member 218, wire 30I, resistor 302, the winding of relay 2 I6, wire 303 and wire 283 to the battery return wire H9 for maintaining the relay 2I6 energized. Also, a circuit is completed from the battery supply wire 229 through wire 322, resistor 323, back contact member I36 of relay I01 in its down closed position, wire I31, binding post I44, lead I42, resistor I38, lead I43, binding post I45, wire I39, back contact member l41 in its down closed position, and wire 234 to the battery return wire H9, for the purpose of keeping the;

temperature compensating resistor I38 heated to compensate for the heating of andthe consequent change in resistance of the release control circuits in the train on the third branch of the bridge arrangements 93 which are constantly energized under the control of master switch device 5 during a straight-air brake application.

Also when there is a straight-air brake application the common wire 212 will be energized and the voltage drop across the resistor H4 will be sufiicient to maintain winding 245 of relay 238 energized and keep the contact members 256 and 251 in a closed position. The contact arm 249 of resistor 248 is positioned in correspondence with the contact arm I59 of resistor I58, as by connection through a common shaft, indicated by the broken line in Fig. 2 of the drawing for the purpose of varying the resistance in series with winding 245 of relay 238 according to the actual number of cars in the train. The resistance of that portion of resistor 248 included in series with winding 245 of relay 238 and subject to the voltage drop across rcsistor H4 is thus automaticallyw adjusted so that the current energizing the winding 245 while only the release control circuit is energized, is slightly in excess of that required to maintain the relayin its picked-up.

position, for any given number of cars in thenot result in a drop-out of the relay 238. Sim- I ilarly the occurrence of such a fault on only the application control circuit, during a brake apj-r plication, as causes either an increase or are duction of currentin the return wire 212 will not efiect a drop-out of relay 238. It will thusbe seen that during a brake application, relay 238 will-be restored automatically to its dropped-out position; as a result of only such faults as occur on the" release control circuit and causing a reduction of the current in return wire 212 and a corresponde ing reduction in the voltage drop across resistor.

H4 below that required to energize the windings 245 of relay 238 sufiiciently to maintainthereen lay in a picked-up position. a

Contact member 251 of relay 238 effective;

when thus restored to its dropped-out or open, position, to break the circuit described in a pre-- vious paragraph forenergizing relay 216 and holding contact members 22! and 220 of relay 2I6 in a picked-up closed position. Contact members 22! and 220 consequently move to the down closed position, thereby establishing the circuits for energizing the warning signal lamps 259 and 26I and the warning buzzer 320 by the circuits ly described.

The contact member 256 of relay 238 is efiective when restored to its dropped-out or open position i to open the local loop circuit for discharging con-- denser 304 so that the condenser 304 will be un-'- able to discharge through the winding of relay- 2I6, thus causingan instantaneous dropping-out of relay 2I6 when a fault occurs during a brake 5 application. a

The front contact member 2 I9 of relay 2I6 is closed except during a fault indication when the relay 2 I 6 is dropped out or deenergized. The con-; tact member 2I9 is included in parallel with the contact member 269 of the pneumatic switch 268- in a circuit for energizing the winding 43 of magnet valve device 4 which circuit extends from the positive terminal of the battery supply 60 to; the speed responsive switch 9|, wire 214, terminal post 263, contact member 2I9, terminal post-264;; wire 213, the winding 43 of the magnet valve de vice 4 and thence to the wire 14 which is'con-i nected to the negative terminal of the battery supply 60. The speed-responsive switch 9| is con- 7 trolled and operated by means not shown and'not part of this invention, so as to automatically in? terrupt this justdescribed circuit at a selected high speed of the train and thus cause an auto-' matic application of the train brakes ina manner presently described. The contact member 2690f switch device 268 is actuated to its open position when a predetermined fluid pressure, such as 10 pounds per square inch, is established in the straight-air control pipe II. Thus, while a fault indication is given'by the circuit checking ap paratus and the contact member 2 I 9 is in its ;open position, if the operator attempts to make' 'a straight air brake application, the actuationfof contact member 2690f switch 268 to its open 'posij-f' tion, opens the cir'cuitenergizing the winding of magnet valve device 4-. -LThe chamber 33 ofthe vent valve device 3 is-thereby-ventedand, as pre age-ran vioiisly described, an automatic brake astutetion is efiected by the venting of fluid pressure from the brake pipe by operation of the vent valve device.

If so desired, the switch device 268 may be disconnected from its circuit or omitted. In such case, the energizingcircuit for the magnet valve device 4 is opened immediately upon the restoration of contact member 219 to open position upon afault indication, thus causing an automatic brake application at the time the fault occurs without waiting until a straight-air brake application is initiated.

Normally, an intermittent fault which lasts for a sufficient length of time to cause deenergization of relay 216 will result in continued deenergization of this relay unless the winding of relay 216 is restored by manual operation of switch 110. Similarly, a fault which is self-correcting after a short interval of time suflicient to cause deenergization of relay 216 would normally result in continued deener'g'ization of this relay unless restored by manual operation of switch 110. If such faults exist, it might prove very inconvenient to the operator to repeatedly operate the switch 116 to restore the relay 216 to. its energized condition especially if the equipment case 94 and thus the switch 110 were located in a position remote to the operators station in the locomotive. two terminal posts 326 and 321 on the equipment case 94 are connected to opposite terminals of the switch including the contact member 266 of the switch device 110 and to opposite terminals of the switch including contact member 218 of relay 216 by wires 328 and 361, respectively. A push-button type switch 325 may be connected to these terminal posts 326and 321 and located at any place convenient to the operator and thus provide for a more convenientmanual restoration of the energization of the relay 216 in case of such intermittent faults, by a manner presently described. After the fault is corrected, if it is a self-correcting fault, or during the interval when the train control circuits are unimpaired if the fault is intermittent, the switch 325 is operated so as to connect the two terminals 326 and 321 together to complete a circuit from wire 293 which is connected to battery supply as previously described, to wire 328, switch 325, wire 301, resistor 362, the winding of relay 216, wire 303, and wire 283 to the battery return wire 119 which will energize and restore relay 216 to its picked-up position, in which position the fault indication circuits are deenergized and the clear indication signal lamps 258 and 261 are energized by circuits previously described. An alternate means for effecting a completion of the above described circuit is to substitute for the push-button switch 325, a jumper wire (not shown) extending from the terminal post 326 to the terminal post 321. By allowing a jumper wire to continuously connect the terminal post 326 to the terminal post 321 it is apparent that if such an intermittent or self-correcting fault would occur, the relay 216 would be restored to its picked-up position automatically when the fault is corrected and the relays 113 and 116 are operating normally.

It should be understood that while my invention has been disclosed specifically in connection with two control circuits it is not limited in its operation to any particular number of control circuits. It may be adapted by the addition or subtraction of bridge arrangements and detector To provide for such instances,

mm to operate with number creontisl air;

cults to control the coding relays.

Having now described my invention; what 1 claim as new and desire to secure by Letters Pat'- ent, is:

1. For use in connection with a vehicle brake control circuit, apparatus for signaling the in tegrity of the brake control circuit, said appa= ratus comprising a first means responsive to the brakes are released or applied for indicating the integrity of the brake control circuit.

2. For use in connection with a vehicle brake 1 control circuit, apparatusfor signaling the-in-- tegrity or lack of integrity oi the brake control circuit; said apparatus comprising a f rst means responsive to the integrity or lack of integrity of the brake control circuit while the brakes con trolled thereby are released, a second means re'-' sponsive to the integrity or lack-of integrity of the brake control circuit while the brakes con trolled by the brake circuit are applied, and means controlled automatically by said first or said second means depending upon whether the brakes are released or applied for indicating the integrity or lack of integrity of the brake control circuit. 7

3. For use in connection with a plurality of brake control circuits cooperatively functioning to control the application and release of the brakes on a vehicle, apparatus for signaling the integrity or lack of integrity 'of the brake control circuits said apparatus comprising a first means responsive to the integrity or lack of integrity or all of said brake control circuits while the brakes controlled thereby are released, an ele'ctro-re sponsive means responsive to the integrity or lack .of integrity of only one of said brake control circuits while the brakes controlled by said brake control circuits are applied, and means controlledautomatically by said first means or by said elec-' tro-responsive means; depending upon whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuits or of said one brake control circuit.

4. For use in connection with a plurality of brake control circuits cooperatively functioning to control the application and release of the brakes on a vehicle, apparatus for signaling the integrity of the brake control circuits, said apparatus comprising a Wheatstone Bridge arrangement for each control circuit, each bridge arrangement including a corresponding control circuit as a branch thereof, a branch including a variable resistor unit adjustable to conform to the resistance of the corresponding control circuit to produce a balanced condition or that bridge arrangement when the brakes subject to the control of that brake control circuit are released, electrical means responsive to the balanced condition of the bridge arrangement for each control circuit to effect an intentional unbalanced condition thereof and responsive to the intentional unbalanced condition of the bridge arrangement to restore the balanced condition thereof as long as no -'f-ault occurs on said brake control circuit while the brakes controlled thereby are released; additional means responsive to the integrity of one er the brake control circuits aura-442 while the brakes subject to the control of the brake control circuits are applied; and means selectively controlled automatically by the electrical means of said Wheatstone Bridge arrangements or by said additional means, depending upon whether the brakes are released Or applied, for indicating the integrity of the said brake control circuits or of said one brake control circuit.

5. For use in connection with a vehicle brake control circuit, apparatus for signalin the integrity or lack of integrity of the brake control circuit, said apparatus comprising a first means responsive to the integrity or lack of integrity of the brake control circuit while the brakes controlled thereby are released, an electro-responsive device effective when energized by current exceeding a certain value to have one position and when energized by a current below said certain value to have a different position, means associating said electro-responsive device with the said control circuit in such a manner as to cause said electro-responsive device to be energized when the brakes controlled by said circuit are applied, by a current exceeding said certain value as long as the integrity of the control circuit is not impaired and for causing said electroresponsive device to be energized by a current below said certain value when the integrity of the control circuit is impaired; and means controlled automatically by said first means or by said electro-responsive device depending upon whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuit.

6. For use in connection with a brake control circuit for a train of cars, apparatus for signaling the integrity or lack of integrity of the brake control circuit, said apparatus comprising a first means responsive to the integrity or lack of integrity of the brake control circuit while the brakes controlled thereby are released, an electro-responsive device effective when energized by current exceeding a certain value to have one position, and when energized by a current below said certain value to have a different position, means associating said electro-responsive device by a current exceeding said certain value as long as the integrity of the control circuit is not impaired and for causing said electro-responsive device to be energized by a current below said certain value when the integrity of the control circuit is impaired, a variableresistor unit preadjustable according to the number of cars in the train, to conform to the normal resistance of the brake control circuit existin when the brakes controlled thereby are applied, to adjust the current delivered to said electro-responsive device to a said certain value for operating said electro-responsive device, as indicated in last said means; and means controlled automatically by said first means or said electro-responsive device, depending upon whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuit.

7. For use in connection with a plurality of brake control circuits cooperatively functioning to control the application and release of the brakes on a vehicle, apparatus for signaling the integrity and lack of integrity of the brake control circuits, said apparatus comprising a Wheatstone Bridge arrangement for each control circuit, each bridge arrangement including a corresponding control circuit as a branch thereof, a branch including a variable resistor unit adjustable to conform to the resistance of the corresponding control circuit to produce a balanced condition of that bridge arrangement when the brakes subject to the control of the brake control circuits are released, electrical means responsive to the balanced condition of the bridge arrangement for each control circuit to effect an intentional unbalanced condition thereof and responsive to the intentional unbalanced condition of the bridge arrangement to restore the balanced condition thereof as long a no fault occurs on said brake control circuit while the brakes controlled thereby are released; a relay means having a winding ffective when energized by current exceeding a certain value to maintain the relay means in one position and when the current reduces below said certain value to cause operation of the relay means to a different position, means for causing the winding of said relay to be energized by a current exceeding said certain value as long as the integrity of one of the said control circuits is not impaired and for causinga reduction of the current energizing the said winding to below said certain value when the integrity of the said one control circuit is impaired, and means controlled automatically by the electrical means of said Wheatstone Bridge arrangements or by said relay means, depending upon whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuits or of said one circuit.

8. For use in connection with a plurality of brake control circuits cooperatively functioning to .control the application and release of the brakes on a train of cars, apparatus for signaling the integrity or lack of integrity of the brake control circuits, said apparatus comprising a Wheatstone Bridge arrangement for each control circuit including a corresponding control circuit as abranch thereof, a branch including a variable resistor unit adjustable to conform to the resistance of the corresponding control circuit to produce a balanced condition of that bridge arrangement when the brakes subject to the control of that brakecontrol circuit are released, electrical means responsive to the balanced condition of the bridge arrangement for each control circuit to effect an intentional unbalanced condition thereof and responsive to the intentional unbalanced condition of the bridge arrangement to restore the balanced condition thereof as long as no fault on said brake control circuit occurs while the brakes controlled thereby are released; an

electro-responsive device effective when energized by current exceeding a certain value to have one position, and when energized by a current below said certain value to have a different position; means for causing the electro-responsive device to be energized by a current exceeding said certain value as long as the integrity of one of said control circuits is not impaired and for causing a reduction of the current energizing the said electro-responsive device to below said certain value when the integrity of the said one control circuit is impaired; a resistance variable according to the number of cars in the train to so conform to the normal resistance of the brake control circuit existing when the brakes controlled thereby are applied, as to provide substantially the same current for energizing said electroresponsive device under no fault and fault conditions respectively, notwithstanding variation in the number of cars in the train and means con- 7 trolled automatically by the electrical means of 31 said Wheatstone Bridge arrangement or by said electro-responsive device, depending upon'whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuits or of said one control circuit.

9. For use in connection with a brake control circuit operatively controlling the application and release of the brakes on a train of cal-shavinga brake system which includes an application control circuit and a release control circuit, apparatus comprising a Wheatstone Bridge arrangement adapted to receive the application control circuit as a branch thereof, and a second Wheatstone Bridge arrangement adapted to receive the release control circuit as a branch thereof, each bridge arrangement further including as a second branch thereof a resistor unit adjustable to conform to the resistance of the corresponding control circuit to produce a balanced condition of that bridge arrangement while the brakes controlled by the brake control circuits are released, a third and a fourth branch each including a fixed resistor, electrical means responsive to the balanced condition of the bridge arrangement for each control circuit to effectwan intentional unbalanced condition thereof, and responsive to the intentional unbalanced condition of the bridge arrangements to restore the balanced condition thereof as long as no fault occurs on said brake control circuits while the brakes controlled thereby are released, a temperature compensating resistor in said fourth branch of each bridge arrangement subject to atmospheric temperature and having an electrical characteristic such that it compensates for changes in the corresponding control circuit resistance, due to atmospheric temperature changes, in a manner to prevent undesired unbalance of the bridge arrangements, means for deenergizing both of said bridge arrangements while the brakes subject to'the control of the said control circuits are applied, means for separately energizing the temperature compensating resistor for said second Wheatstone Bridge arrangement, when the brakes controlled by the brake control circuits are applied, to cause heating thereof in correspondence with the heating of the release control circuit when the brakes are applied, in a manner to prevent undesired unbalance of that bridge arrangement when the brakes controlled by the brake control circuit are released after an application, and means controlled automatically by said electrical means of said first and second 'Wheatstone Bridge arrangements when the brakes are rleased for indicating the integrity of the brake control :circuits.

10. For use in connection with a brakercontrol circuit 'operatively controlling the application and release of the brakes on :a train of cars :havingabraking system which includes :an application control circuit and a release control circuit, apparatus comprising a Wheatstone Bridge arrangement adapted .to "receive the :application control circuit asa branch thereof and a second Wheatstone Bridge arrangement adapted to :receive the release control circuit :as :a branch thereof, each bridge arrangement further including as -a second ibranch thereof :a resistor unit adjustable to conform to. the resistance .of the corresponding control :circuit :to produce a :bal-

anced condition of that bridge arrangement while the brakes controlled by the :brake control circuits are released, a third branch and a fourth branch each including a fixed resistor, electrical means ''responsive to the balanced condition I of the bridge arrangement for each control circuit to effect an intentional unbalanced condition thereof and responsive to the unbalanced condi:- tion of the bridge arrangement to restore the balanced condition thereof as long as no fault ocours on said brake control circuits while the brakes controlled thereby are released, a temper.- ature compensating resistor in said fourth branch of each bridge arrangement subject to at!- mospheric temperature and having an electrical characteristic such that it compensates for changes in the corresponding control circuit re sistance, due to atmospheric temperature changes,- in a manner to prevent undesired un-- balance of the bridge arrangement, means for deenergizing both of said bridge arrangements while the brakes subject to the control of the said control circuits are applied, means -for separately energizing the temperature compensating resistor for said second W heatstone Bridge arrangement, when the brakes controlled by the brake control circuits are applied, to cause heating thereof in correspondence with the heating of the release control circuit when the brakes are applied, in a manner to prevent undesired unbalance of that bridge arrangement when the brakescontrolled by the brake control circuit are released after an application, electro-responsive means responsive to the integrity of one of said brake control cir-' cuits while the brakes controlled by the brake control circuits are applied, and means controlled automatically by either said electrical means of said first and second Wheatstone Bridge arrangements, or by said electro-responsive means :de pending upon whether the brakes are released or applied, for indicating the integrity of the'brake control circuits or of said one brake control circuit.

11.:Eor use in connection with a plurality .of vehicle brakecontrol circuits, the combinationof a first means responsive to the integrity of'ithe brake control circuits while the brakes controlled thereby are released, a second means responsive to the integrity of one of said brake control circuits while "the brakes con-trolled thereby are ap:- plied, means responsive to energizationpf said one brake control circuit incidental to initiation of a brake application for automatically rendering said first means ineffective and said second means effective, and responsive to thedeenergization of said one brake control circuit incidentalto a brake release for automatically rendering said first means eiiective and said sec ond means ineifective, and rneanscontrolled automatically by said first or said second means, depending upon whether the brakes are released or applied, for indicating the integrity of the brake control circuits orof said one control circuit.

12. For use'in connection with a plurality of vehicle brake control circuits, the combination of a first means responsive to the integrity of the brake control circuits while the brakes controlled thereby are released, a second means responsive to the integrity of one of said'brakecontrol circuits while the brakes controlledthereby are applied, means responsive to the energization of said one brake control'circuit, incidental to initiation of brake application, for automatically rendering said first means ineffectiveand said second means effective, and responsive tothe deenergization of said one brake control circuit'incidental to a brake release for automatically rendering said first means effective and said :second =means ineffective, and a single means con- 33 trolled automatically by either said first or said second means, depending upon whether the brakes are released or applied, for indicating the integrity of the brake control circuits or of said one control circuit.

13. For use in connection with vehicle brake control circuits, the combination of a first means responsive to the integrity or lack of integrity of the brake control circuits while the brakes controlled thereby are released, a relay having two separately energizable windings, one of said windings being effective when energized to cause pick-up of said relay and to maintain said relay picked-up, and the other of said windings being effective only when energized by a current exceeding a certain value, for maintaining the said relay pick-up, means for energizing said one winding only while the brakes controlled by the brake control circuits are released, means for energizing the other of said windings by a current exceeding said certain value only when the brakes controlled by said brake control circuits are applied and the integrity of one of said control circuits is not impaired, and signal means controlled alternatively by said first means or by said relay, depending upon whether the brakes are released or applied, for indicating the integrity or lack of integrity of the brake control circuits or of said one control circuit.

14. For use in connection with vehicle brake control circuits on a train of cars, the combination of a first means responsive to the integrity or lack of integrity of the brake control circuits while the brakes controlled thereby are released, a relay having two separately energizable windings, one of said windings being effective when energized to cause pick-up of said relay and to maintain said relay picked-up, and the other of said windings being eifective only when energized by a current exceeding a certain value for maintaining the said relay picked-up, means for energizing said one winding only while the brakes controlled by the brake control circuit are released, means for energizing the said other winding in accordance with the current in one of said brake control circuits and by a current exceeding said certain value only when the brakes controlled by said brake control circuits are applied and the integrity of said one brake control circuit is unimpaired, variable resistance means preadiustable according to the number of cars in the train to adjust the current in the said other winding to a value in excess of said certain value, notwithstanding variation in the number of cars in the train, as long as the integrity of the said one brake control circuit is not impaired, and a signal means controlled alternatively by said first means or by said relay, depending upon whether the brakes are released or applied, for indicating the integrity or 34 lack of integrity of the brake control circuits or of said one control circuit.

15. For use in connection with an electric circuit, the combination of a relay having two separate windings, one of said windings being effective when energized to cause pick-up or said relay and to maintain said relay picked-up, and the other winding being efiective only when energized by a current exceeding a certain value for maintaining the said relay picked-up, means for energizing said one winding and deenergizing said other winding when said circuit is deenergized and for deenergizing said one winding and energizing said other winding when said circuit is energized, variable resistor means preadjustable to adjust the current in the said other winding to a value in excess of said certain value, notwithstanding variation in the resistance of the control circuit, as long as the integrity of the said control circuit is not impaired, and signal means controlled by said relay for indicating the integrity or lack of integrity of the said circuit while it is energized.

16. For use in connection with a plurality of brake control circuits cooperatively functioning to control the application and release of the brakes on a vehicle, the combination of a Wheatstone Bridge arrangement for each control circuit, each bridge arrangement having a fixed resistor as one branch thereof, a second branch including a fixed resistor, a third branch including the corresponding control circuit, a fourth branch including a variable resistor, electrical means responsive to the balanced condition of all said bridge arrangements to eifect an intentional unbalanced condition thereof by alternatively intentionally short-circuiting either the said one branch and said third branch of each bridge arrangement simultaneously or said second branch and said fourth branch of each bridge arrangement simultaneously, and responsive to the intentional unbalanced condition thereof to restore the balanced condition thereof as long as no fault occurs on said brake control circuits, and means controlled by said electrical means for effecting an indication of the integrity of the brake control circuits.

CLAUDE M. HINES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,052,190 Miller et al Aug. 25, 1936 2,055,563 Sorensen et a1. Sept. 29, 1936 2,091,007 McCune Aug. 24, 1937 2,276,706 Sorensen et a1 Mar. 17, 1942 2,478,000 Miller Aug. 2, 1949 

